Give the structures of the intermediates represented by letters K and Q in this synthesis.

Verified step by step guidance

1. Step 1: Analyze the starting material, which is an ester (phenylpropanoate). The first reaction involves LiAlH4 in ether followed by H3O+. This is a reduction reaction that converts the ester into a primary alcohol. The intermediate labeled 'J' is the primary alcohol formed from the reduction of the ester.
2. Step 2: The alcohol 'J' is treated with TsCl (tosyl chloride) in pyridine. This reaction converts the alcohol into a tosylate, which is a good leaving group. The intermediate labeled 'L' is the tosylate derivative of the alcohol.
3. Step 3: The tosylate 'L' undergoes elimination with KO-tBu (potassium tert-butoxide), a strong base. This results in the formation of an alkene via an E2 elimination mechanism. The intermediate labeled 'M' is the alkene formed.
4. Step 4: The alkene 'M' is treated with Br2 followed by H2O. This is a halohydrin formation reaction, where bromine adds across the double bond and water attacks the more substituted carbon. The intermediate labeled 'N' is the halohydrin formed.
5. Step 5: The halohydrin 'N' is treated with TIPS-Cl (triisopropylsilyl chloride) and Et3N (triethylamine). This reaction protects the hydroxyl group by converting it into a silyl ether. The intermediate labeled 'O' is the silyl-protected halohydrin.

Key Concepts

Synthesis Pathways

Synthesis pathways illustrate the step-by-step transformation of reactants into products through various intermediates. Understanding these pathways is crucial for predicting the structure of intermediates, as each step often involves specific reagents and conditions that dictate the outcome of the reaction. Familiarity with common reactions, such as reductions, oxidations, and substitutions, is essential for interpreting the diagram and identifying the intermediates labeled A to Q.

Functional Groups

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. In organic synthesis, recognizing functional groups such as alcohols, aldehydes, ketones, and ethers is vital for understanding how intermediates will behave during reactions. The presence of these groups influences reactivity and the types of transformations that can occur, which is key to deducing the structures of intermediates in the synthesis pathway.

Reagents and Conditions

The choice of reagents and reaction conditions significantly affects the course of a chemical reaction and the formation of intermediates. For example, reagents like LiAlH4 are strong reducing agents, while TsCl is used for activating alcohols for substitution reactions. Understanding the role of each reagent and the conditions under which they operate helps in predicting the structures of intermediates and the overall success of the synthesis process.